In digital transmission systems, and particularly in local area networks (LANs), it is common to connect a plurality of stations together by a common transmission medium. In such systems, each station transmits digital data on the common transmission system, one at a time, and the remaining stations must wait until the medium is idle before starting a transmission. To assist in assigning the common transmission medium to the stations, elaborate protocols are often used, sometimes invoking a master station which enforces access priorities by assigning the transmission facility to the stations in a preselected order. Such elaborate protocols increase the overhead in operating such a system and reduce the data throughput proportionally.
Data transmitted on such local area networks has usually been divided into equal-sized packets. Such packets are usually kept to a reasonable size to give other stations a fair opportunity to seize the common line for transmitting their own message packets. The packet size, however, is arbitrary in terms of the actual needs of the transmitting stations and requires wasteful padding of unused portions of the packet for short messages or dividing large messages arbitrarily into a number of packet-sized pieces. Both message padding and message segmentation reduce the overall throughput of the transmission system.
Finally, since the transmission medium is used in common by a plurality of stations, only two stations can be interconnected at any one time. When in use, all other stations must wait until the transmission path is idle before initiating their own message transmissions.